Son of a *&(#$@!!! Freckles of rust showing through paint on my firewall....

I finished painting the firewall before there was ANY humidity...long before the wet season came. I've installed the engine, done all the wiring, have the inner fenders in place, started bolting the fenders and front group on... I can't believe this. What the heck do you put on bare metal to avoid this ****!! Damn I'm tweaked over this...

 

Do you have any pics?

 

Could it be grinding sparks that landed on the paint?

 

I'll take pics this weekend. I'm just disgusted...like a kick in the groin. So much work that has to be redone because I apparently didn't prep correctly.

 

epoxy primer over bare metal.

 

Very strange for rust to appear through freshly painted metal. Are you sure it's rust? What paint did you use? Is it porous? Is the firewall getting wet to allow the rust to grow?

 

did you get all the rust off the firewall before you painted? how did you clean it? wire wheel? sandblast?

you have to get ALL the rust off first , because rust never sleeps

 

If you used sand as a blasting media, it may be the possible cause. Many times the sand media also contains caustic salts that will start the rust process under your paint.

 

Etching primer then high build if you need it then primer/sealer and paint after that. Or if you are doing rattle can rustolium makes a primer to go over rusted metal that will seal it up. I have some on my Willys that has been on there out in the weather for 3 years and no rust comming through it. It is not a rust converter I think it is an epoxy.

 

Paint each rust flake silver, tell everyone you metalflaked

 

I wire brushed and used purple 3M disc to remove the old paint. I didn't look like there was much rust in those areas before I stripped the paint and definitely didn't see any rust or anything that looked like it would rust after it was stripped. I didn't use a self etching because I primed right away and only had the whole firewall in primer for about 3 weeks during the hot summer before it was painted. I guess I'll be redoing the firewall when I get to the point of final paint.

 

When you wire brush you can work in some contaminates,little pieces of the wire wheel can be imbedded in the metal and will rust very quickly.

I prefer sandblasting,,but you have to use a degreaser,,a specific cleaner designed for prepping metal before you prime and you clean it over and over until your rag is clean.

I always tack it before applying a self etching primer and then lightly sand,,prep it again to rid the surface of any sanding residue and oil from finger prints,,tack and then paint. HRP

 

I ground on some bush hog blades in the vice once and a car was parked close by-- a few days later I noticed it had rust freckles on the hood. It was from the grinding sparks . I took a buffer to it and cleaned it up. Just a thought

 

Someone mentioned epoxy primer? I used that on my engine compartment and I'm seeing a little surface rust here and there. Looks like I didn't get enough paint on it but now Im not sure.

 

I would be picking grinding sparks, could be you we're grinding near by on something else.
Have you tried some rubbing compound to see if they are only on the surface.

 

X2, it'd be the first thing I'd check

 

Based on your description you skipped a critical step in the pre-paint prep
Read the description and it should tell you why it's important. This isn't the only brand, just an example of a phosphoric acid based prep product. Etch prime is a decent second choice, but this is more thorough if done correctly. http://www.aircraft-spruce.com/catalog/cspages/metalprep.php

 

Just curious what type of primer you used prior to paint and how many coats of color ?

 

That's ****s man. I'm getting ready to do my fire wall and inner fenders

 

metalprep, metalprep, metalprep.

matt

 

I like the idea of metal prep but some are very p***ionatly against it. You do be have to be careful of the primers compatability with it. If the primer has any acid in it (etching primer) it will react with metal prep and fail. The tech sheet for Kirker epoxy recomends thd use of their metal prep which I'm sure is just a phospheric acid solution.

 

How clean and dry is your air supply?

 

i did not know that, all my bodyguy friends use it religiously, i buy and use what they tell me so they must know what is compatible. thank you for the tip!

matt

 

Por-15's label on the can of "Rust Preventive Paint" insists on using their Metal Prep beforehand. I am reluctant to do so, and think it is more of a marketing scheme to buy more of their product. Seems like wax and grease remover would be enough if the metal is in good shape.

 

Metal prep is old hit n miss **** that might work ****. All i've ever done is a very fresh machine sand with 150 , blast the hard to get corners and a light coat of zinc chromate primer. Don't let the freshly sanded area sit for longer than 20 minutes or resand it. Let the zinc chromate flash only not dry before you top coat with primer. Trick is to let the zinc bite in before top primer and the top primer will remelt into the zinc. Stick like sh!!! to a blanket. Use this on chrome to or plastic.

 

I've always metalprepped , washed and dryed , prime with Valspar Direct To Metal . no problems in the last 10 years . Ask your local paint rep and try to stay with the same system , and don't buy cheap materials . It'll bite your *** i the end !

 

The most important thing is making sure the metal is clean. If there's any rust to begin with I'd sand blast it, clean and strip discs work well too if the rust pits aren't too deep. Next thing I'd do before priming it is clean it reeaalll good with a surface cleaner, something like Martin Senour's kleanz-ez and a red scotch-brite. For priming I always use self etching primer, after the etch then it's time for either high build primer or seal and paint.
Hope this helps!

 

I just had a thought.....I haven't seen this on any of my builds, but I have seen it on others. Doing a firewall is painting in a dirty place, especially if you've been welding and grinding in the area. I've seen when guys don't do a really thorough cleaning of the area, when they paint, at some point, they get a mess of junk blown up out of some crack or crevice, and it lays in the paint. They dont' worry because another coat of color covers it. Much later, when the paint shrinks a bit, they get a texture in the paint, and sometimes rust spots, as the paint shrinks away from the debris and exposes bits of steel grit/powder.
Did you notice anything like this when you were shooting the firewall?

 

I'd bet money he has some grind sparks that have landed ON that paint and have since rusted....try the hand rub on a spot and check.....

 

Without seeing pics, I would agree with several others above. It may very well be grinding dust that has landed on the surface and rusted. This is especially possible if you have a light color car. I would try and clay bar treatment in one of the areas and see what that does. Even if you have a little of some sort of other rust happening, the clay bar might do the trick. Pics???